It is proposed to systematically develop stereospecific and general methods for the synthesis of exocyclic alkenes, that are applicable to the preparation of both E and Z isomers, based on stereo- and regioselective carbometallation reactions of alkynes. Four conceptually different approaches that are complementary to each other will be investigated. Despite the growing significance of various stereodefined exocyclic alkenes of medicinal interest, such as prostacyclin, carbacyclin, zoapatanol, pumiliotoxin B, and fusidic acid, synthetic chemists are still without general and selective methodologies that can readily provide satisfactory procedures for efficient and selective syntheses of various types of exocyclic alkenes without requiring separate developments of specific procedures for individual cases. The proposed investigation is expected to provide, for the first time, such a general and selective methodology. In part to provide novel, efficient, and stereoselective procedures and in part to demonstrate the practical usefulness of the above-mentioned methodology, carbacyclin and pumiliotoxin B will be synthesized using the above-mentioned methodology.